A re-investigation of Chrysotila (Prymnesiophyceae) using material collected from the type locality.

We isolated 17 strains of Chrysotila stipitata and 10 strains of Chrysotila lamellosa from samples collected at exposed chalk surfaces, Westgate, Kent, England, which is the type locality for C. stipitata (generitype) and C. lamellosa. The nuclear-encoded small subunit and large subunit rRNA were used in a molecular phylogenetic analysis. We also examined the cells using light microscopy. Chrysotila stipitata had two chloroplasts per cell, as originally described, and it was positioned within the Coccolithales (Prymnesiophyceae) in a RAxML tree. Chrysotila stipitata gene sequences formed a clade with Pleurochrysis, and because Chrysotila has priority, Pleurochrysis was placed in synonymy. New nomenclatural combinations were also made. Chrysotila lamellosa was located within the order Isochrysidales, and like other members of the order, C. lamellosa had one chloroplast per cell. We reinstated the generic name Ruttnera to accommodate this species (Ruttnera lamellosa comb. nov.). We also showed that several other taxa described from the chalk cliff type locality were alternate life stages for C. stipitata, and we assigned these as synonyms of C. stipitata. [ABSTRACT FROM AUTHOR]